Pre-exposure prophylaxis (PrEP) refers to daily or intermittent oral administration of antiretroviral drugs designed to protect high-risk HIV-negative individuals from infection. As PrEP is, at present, the most promising biomedical HIV prevention tool, the Centers for Disease Control and Prevention (CDC) released interim guidance for health care providers in January 2011, and is expected to soon release detailed public health guidelines for its use. However, in order for PrEP to become an effective prevention tool, three critical factors must be addressed: a) acceptability, i.e., individuals who would benefit from PrEP must know about it and be willing to take it; b) adherence, i.e., individuals who choose to PrEP as a prevention strategy must take the pills as prescribed; and c) implementation, i.e., processes and protocols must be developed to allow for the integration of PrEP delivery and programs into real world settings in a way that is feasible, scalable, and realistic. The proposed project is a two-phase study, conducted in collaboration with the largest LGBT community health provider in New York City (NYC). This project will focus on three specific aims: 1) Identifying social and behavioral factors that are likely to influence PrEP implementation, acceptance, and use/adherence by MSM in NYC, including factors at individual-, community-, and organizational-levels; 2) Examining social and behavioral factors associated with disparities in access to prevention and care services among MSM in NYC that might directly impact PrEP implementation programs and policies; and 3) Evaluating an intervention in which PrEP is introduced, provided, and supported as part of a prevention package delivered in an community health center. To achieve these aims, the project will enroll high-risk MSM to test a two-stage behavioral intervention. First, eligible participants will be randomized to receive either basic information about PrEP availability or a targeted intervention designed to increase PrEP uptake. Second, participants who accept PrEP (regardless of condition) will be randomized to receive either basic adherence information or an enhanced PrEP adherence intervention. Participants will be followed quarterly for 12 months. Outcome variables will include: PrEP uptake, PrEP persistence, PrEP adherence (measured through self-report and biological measures), STI incidence, and self-reported risk behavior. The project is particularly innovative in that it combines an efficacy and effectiveness trial, testing a new intervention in the setting in which it would most feasibly be delivered, and pioneering a new approach to community-based collaboration and study design that can accelerate the pace of implementation science. The proposed project has the potential to exert a sustained and powerful influence not only on the effectiveness of PrEP interventions for MSM, but also on dissemination and scalability of a targeted intervention within community-based settings and in a manner that reduces disparities in access and maximizes cultural competence and acceptability.